Implants such as an artificial joint and an internal fixation material have been widely used in the field of orthopedic surgery.
Resistance becomes extremely high when, for example, staphylococci and E. coli form a bio film on the surface of an implant, which makes it difficult to perform medical treatment. Thus, the implant needs to have an antibacterial property.
Examples of typically known surface treatment methods of providing the antibacterial property include a method of coating the implant surface with a metal layer made of, for example, silver or iodine, which is antibacterial, to dissolve out metal ions, a method of performing sustained-release of antibiotic substance, and a method of coating the implant surface with an antibacterial compound such as fluorine-based resins.
However, the methods of dissolving out metal ions and antibiotic substance have difficulties in maintaining the antibacterial property in a body for a long duration, and potentially cause toxicity and allergy. In addition, an antibacterial film wears due to friction between the implant surface and a bone or a surgical instrument during or after a surgery, which deteriorates the antibacterial property.
Screws and spinal cages as implant materials in the field of orthopedic surgery are expected to fuse with bones immediately after a surgery so that the duration of medical treatment is reduced and loosening of the screws, shift of the cages, and the like are prevented. Thus, coating provided on the surface of a screw or the like needs to have a high osteoconductive property.
A film containing diamond like carbon (hereinafter referred to as “DLC”) has excellent wear resistance, friction resistance, chemical resistance, and corrosion resistance and high hardness, and thus is widely used as a protective film for a tool, a mold, a machine component, or the like. It is known that an F-DLC film obtained by adding fluorine to DLC has antithrombogenic and antibacterial properties for human body tissues such as muscle, blood, and blood vessels due to the characteristic of fluorine and has excellent biocompatibility.
In addition, it is already known that hydrogen-containing DLC, which contains no fluorine has a high osteoconductive property.
For example, Patent Literatures 1 and 2 disclose technologies of forming an intermediate layer such as a DLC film containing no fluorine on the surface of an implant, and forming an F-DLC film on the intermediate layer.
Patent Literature 3 discloses a technology of forming an F-DLC film on an implant having a surface roughness in a certain range.
In this manner, when the intermediate layer is provided or the implant surface is roughed to achieve an anchor effect, the sticking force of the F-DLC film onto the implant surface increases, which leads to reduction of occurrence of peeling to some extent.